1. Field of the Invention
This invention relates to an automatic printed circuit board tester for testing and diagnosing faults in analog and digital networks and more particularly to an automated fault isolation system for use in trouble-shooting printed circuit boards.
2. Description of the Prior Art
The use of plug-in printed circuit boards in electronic packaging is well known. With the advent of integrated circuits, more complex electronic functions are packaged on a single printed circuit board thus increasing the packing density as well as the complexity of the circuit board. These trends have the potential for decreasing the cost per circuit for a manufacturer utilizing the circuits, since economy can result from the low cost of manufacturing the basic printed circuit board due to the use of automated equipment for plating, etching, drilling, automatic insertion of components in the printed circuit boards, etc. However, with the increase of complexity of the circuits the probability of failure becomes greater, the test and diagnosis of failures assumes a disproportionate part of the manufacturing costs. Accordingly, automated test systems have the potential for reducing test and trouble-shooting costs by speeding up the test and trouble-shooting activity by several orders of magnitude and reducing labor requirements. However, even though the testing activity may be speeded up tremendously so that the printed circuit boards may be classified into good and bad printed circuit boards there still remains the task of isolating where the fault lies in those branches that failed. This in itself is no trivial task. It can be appreciated that because of the complexity of the circuits which may number upwards of hundreds in one printed circuit board the probability of a fault occurrence in some one of these circuits on the printed circuit board is very great-- in the order of 40% of all the circuit boards tested. To isolate and locate a fault by hand probably requires an average of twenty minutes per circuit board. Add to this the inordinate amount of labor, equipment and space to house this labor and equipment and one can appreciate the enormous cost of fault isolation by hand.
What is needed therefore is an automatic printed circuit board tester to test and diagnose faults in printed circuit board networks.